He is about to take up one of the most high-profile posts in football, where unrelenting scrutiny goes with the territory. Yet José Mourinho is as secretive as he is intense, ambitious and complicated. There is a lot he doesn't want to talk about: the sister who died mysteriously, his mother and father, and the comfortable early life he enjoyed as part of a clan that was closely linked to Portugal's far-right dictatorship. Mourinho may be football's coming man but taking over as Chelsea's manager is likely to involve constant prying which will test his combustible nature.

Just three years ago Mourinho, a failed footballer, ex-PE teacher and former interpreter, was in charge of Uniao Leiria, a small Portuguese football club which struggles to attract 2,000 fans to its home games. This weekend he is agreeing thedetails of a contract which will make him the best-paid manager in the game's history at £5 million a year over four years.

Overrated and overhyped the Premiership may be, but it does throw up some sensational off-field storylines: Manchester United Alex Ferguson kicking a boot at David Beckham; the Thai Prime Minister who wants to spend his citizens' money buying a share of Liverpool; leading players accused of rape and other crimes; and Roman Abramovich, the Russian billionaire who since buying Chelsea last summer has spent £250m trying to turn them into the world's best.

To this intriguing cast of characters can now be added the abrasive, swaggeringly confident figure of Mourinho. Still only 41, the gaffering trade's nearest thing to George Clooney is suddenly soccer's hottest managerial property after a mere four years on the job. He has just won five major trophies inside 12 months with Porto, whom he left last week hours after leading them to the European Cup, club football's biggest prize.

Portugal's leading psychiatrist recently suggested that Mourinho is convinced he has been given a special gift of leadership from God. He is certainly religious. On the pitch before every kick-off, he kisses two things: a photograph of his two children, and a crucifix.

An inspirational figure, who clearly excels at organising and motivating footballers, he is about to take charge of the highly-paid, expensively-assembled personnel who wear the blue shirts of 'Chelski'. Stars such as Hernan Crespo, Juan Sebastian Veron and Wayne Bridge may be among those feeling apprehensive at changes the Portuguese will make. They were among the recruits who joined last season when £125m of talent, funded by Abramovich, was meant to make Chelsea champions of Europe, or at least England. Reaching the semi-final of the Champions' League and finishing second in the Premiership was highly creditable, but these days counts as failure in London SW6. Thus very soon Claudio Ranieri, the incumbent manager treated so appallingly by his employers, will finally leave and Mourinho, his replacement, will start spending more - much more - of the oil magnate's money.

The fascination with Mourinho is partly whether he can lead the Blues to bigger glories than Ranieri. But it is also with the changing landscape of football management, and the growing trend that when a top British club needs a new man in the dugout, it looks abroad rather than around Britain, the country that produced Clough, Ramsay, Busby, Stein and Shankly. Witness Liverpool's pursuit of both Mourinho and Rafael Benitez, the Spaniard who has just led Valencia to the La Liga title, to replace Gerard Houllier, a Frenchman. Tottenham Hotspur have considered several foreign coaches. Arsenal, the champions, are under the control of Arsene Wenger, a native of Strasbourg. England will try to win Euro 2004 with Sven Goran Eriksson, a Swede, at the helm.

It is Mourinho's methods, not just his nationality, which make his arrival at Stamford Bridge meaningful. His status as arguably the best-prepared, most tactically astute and most effective man-manager means his modus operandi will set new standards. He seems to boast a range of qualities which rivals have some, but not all, of. While Wenger shares Mourinho's preference for collective team effort over individual brilliance, the former has not devised the defensive strategy needed to capture the European Cup which the latter, an expert in suffocating the opposition, has just done. Celtic's Martin O'Neill displays a similar talent for operating within a tight budget and re-energising players who have slipped into anonymity, yet his team has twice gone out of the Champions' League after the first group stage.

Refreshingly, Mourinho's success reaffirms that, even in an era of £40m transfers and £100,000-a-week salaries, a group of largely-unsung players led by a relative unknown can still triumph. But it is also mysterious. Others put similar emphasis on psychology or detailed pre-match planning, such as videos for his defenders about how an opposing striker moves, so why has none yet found such a potent combination?

'Mourinho is brilliant because of his human qualities. He knows how to extract everything a player has,' says Porto veteran Carlos Secretario. 'I've known him for a long time and he has this special way of organising his players and understanding how they want to play,' offers Victor Baia, the goalkeeper. 'He's a great trainer ... the best coach in Europe and in the world,' added striker Benni McCarthy after Porto's win over Monaco last week.

His achievements are the more remarkable because, while his father kept goal for Portugal, he played football at a low level, as did Wenger and Eriksson. But once he learned at 15 that he did not have the talent to make the grade as a player, he dedicated himself to becoming a coach.

His lucky break came in 1992 when he began translating for Bobby Robson, the ex-England boss, at Sporting Lisbon. They became close and Robson was a mentor. Before long the young man with the PE degree and five languages proved himself so adept at analysing the game that he became part of Robson's team, following him to Porto and Barcelona. 'He learned fast and was very clever. He quickly realised the importance of establishing a rapport with the players,' English football's grand old man, now 71, recalls of the protégé 30 years his junior. 'He'd never been a player at a high level so he respected what they could do. He was a great guy with the players and they appreciated that.' Mourinho for his part admits: 'I owe him for so much. I was a nobody when he came to Portugal.' Since going it alone as a coach in his own right in 2000, Mourinho has proved unstoppable. His Porto, who play in one of European soccer's lesser leagues, are the first team since 1995 to break the stranglehold of the continent's four richest leagues - England, Spain, Italy and Germany - by lifting the European Cup.

A non-conformist from an early age - he neither drank nor smoked - Mourinho is compelling also because he is ... well, different. The self-confessed right-winger from Setubal, with its communist council; handsome object of female attention who has been with the same woman for 24 years; and the ambitious manager who admits his wife Tami, daughter Matilde and son José Mario are more important than the game itself. The upstart who is not afraid to trade verbal blows and pre-match mind games with some of football's elder statesmen.

Personal tragedy looms large in his life. His only sibling, sister, Teresa, died in 1997, aged 37. The official explanation was her diabetes. But others believe the drugs she began using after her marriage broke up caused the infection which killed her. Mourinho refuses to discuss it.

Joel Neto, a Portuguese journalist who recently spent two months researching soccer's coming man, says: 'He's brilliant, very determined to pursue his goals and very tough; I wouldn't want to be his enemy. He doesn't just work with people. He controls people. He dominates people. He works with people's minds.' Yet his players, infused by their manager's own huge self-belief, are a happy, devotedly loyal bunch.

It will be fascinating to see how such a commanding man and control freak fits in at Stamford Bridge where Abramovich, Peter Kenyon, his chief executive, and Pini Zahavi, the agent who acts as his talent-spotter, are all influential figures. Mourinho, who demands the freedom to do things his way, walked out on Benfica when they interfered with his work. He has long wanted to work in England because of the tradition of a powerful manager who is involved in every aspect of the club; in contrast, the coach which is the norm elsewhere in football usually only trains and selects the team.

While Mourinho seem a logical choice to take Chelsea onto a higher level, there are potentially many problems. His manner may upset a football press corps who adore the charming, quotable Ranieri. Fans could rebel if some of their favourites, such as Frank Lampard, are squeezed out. His safety-first style of football will be a shock for fans used to the non-stop excitement of the Premier League. And there is, surely, huge scope for fallouts between 'my way or no way' Mourinho and the equally driven Abramovich.

Then, crucially, there are the players, anxious about their places and reputations, who may also refuse to let the control freak have his own way. Chelsea's players are internationals and World Cup winners, not underdogs with something to prove. At least some will go and others barely feature at all amid a influx of big names. 'He tries to win the heart of the players and if he has to deal with a lot of stars in the Chelsea dressing room, I'm sure he can handle it,' says McCarthy, one of Mourinho's loyal band at Porto. Only time will tell. But whoever acts as interpreter next season between Abramovich and his new manager should probably invest in some earplugs.